1. Field of Endeavor
The present invention relates in general to the art of power beaming and more particularly to a laser power beaming system.
2. State of Technology
There is an active interest in power beaming to air and space borne platforms and the inverse application, beaming converted solar power back to earth. One concept that has been demonstrated is that a helicopter could be kept aloft with a ground based, high power microwave source. Power beaming to satellites for propulsion using jet ablation has been considered. The concept of capturing solar power from a satellite based photovoltaic array, converting that power to microwaves and transmit that microwave power back to earth for commercial uses has been considered. Power beaming using high power lasers to the lunar surface to support a colony has been considered. Power beaming to satellites at Geosynchronous Earth Orbit (GEO) has been considered. The uses of power beaming to GEO include battery charging, space tugs to change orbit, and for primary power to increase the transponder capacity. A program to measure the solar cell conversion efficiency using various lasers was initiated in support of the overall concept of power beaming. A test of power beaming to a low altitude satellite using both liquid and solid state lasers has been considered by one of the inventors.
NASA has initiated a program involving a high altitude aircraft powered by solar power for the purpose of Environmental Research and Sensor Technology (ERAST). The plan is to keep the aircraft aloft during the night using regenerative fuel cells; but these devices are heavy, inefficient, and beyond the present state of the art.
U.S. Pat. No. 5,260,639 to Russell J. De Young, Michael D. Williams, Gilbert H. Walker, Gregeory L. Schuster, and Ja H. Lee, assigned to The United States of America as represented by the Administrator of the National Aeronautics and Space Administration (NASA), shows a method for remotely powering a device such as a lunar rover. A method of supplying power to a device such as a lunar rover located on a planetary surface is described. At least one, and preferably three, laser satellites are set in orbit around the planet. Each satellite contains a nuclear reactor for generating electrical power. This electrical power is converted into a laser beam which is passed through an amplifying array and directed toward the device such as a lunar rover. The received laser beam is then converted into electrical power for use by the device.
In U.S. Pat. No. 3,781,647 to Peter R. Glaser, assigned to Arthur D. Little, Inc., a method and apparatus for converting solar radiation to electrical power is shown. Solar radiation is collected and converted to microwave energy by means maintained in outer space on a satellite system. The microwave energy is then transmitted to earth and converted to electrical power for distribution. Solar radiation is collected and converted to microwave energy by means maintained in outer space on a satellite system. The microwave energy is then transmitted to earth and converted to electrical power for distribution.
In World Intellectual Property Organization (WIPO) Patent Application WO 98/13909, filed Sep. 3, 1997, by John L. Remo, a system for energy transmission by infrared laser radiation is shown. Strong laser beams in the atmosphere are a danger to air travelers and subject to disruption by clouds and other weather and atmospheric conditions. Infrared laser radiation does not pose the danger to air travelers or disruption by clouds and other weather and atmospheric conditions. Infrared laser radiation is produced at a source location. The infrared laser energy is transferred to an energy consuming location. The infrared laser radiation is converted to light at another wavelength at the energy consuming location. The light at the other wavelength is visible and can be converted photoelectrically to electrical energy. The electrical energy is produced by converting the visible light photoelectrically to electrical energy. The infrared radiation used is both eye safe and atmospherically transmissive.
The present invention provides a system for transmitting power between earth and a high altitude platform in sufficient quantities to be useful for various purposes such as powering equipment, propulsion, and other power consuming uses. A power receiving device is utilized to receive the transmitted power. A laser system operated outside of infrared is used to transmit power between earth and the power receiving device. The laser system does not require adaptive optics.
In one embodiment of the invention, power is transmitted from earth to a power receiving device located on a high altitude platform in sufficient quantities to be useful for propulsion, powering equipment, and for various purposes. The power is transmitted by a diode pumped solid state laser system that does not require adaptive optics.
In another embodiment of the invention, power is transmitted between earth and a remote platform at high altitude in sufficient quantities to be useful for propulsion, powering equipment, and for various purposes. A power receiving device is located on the remote platform. Power is transmitted between earth and the power receiving device using an array of individual lasers. Each of the lasers in the array produces a beam with a selected initial beam diameter that will provide an arrival beam with a desired spot size to fit within a desired area and pattern on the power receiving device.
In another embodiment of the invention a radar system has automatic control of the laser beam shutter. The automatic radar uses a phased array antenna to produce a narrow angle beam. The radar beam is boresighted to the laser beam and the parameters arranged such that when an aircraft is detected at the outer edges of the radar beam, the laser shutter is closed before the aircraft can intersect the laser which is in the middle of the radar beam. A video camera, also boresighted to the laser beam, provides a visual record of aircraft passing through the radar beam thereby documenting the laser shutter closure for recording purposes. In addition to aircraft detection, contact is maintained with the US Space Command who transmits satellite passage information so that the laser can be shuttered to avoid intersection with satellites.
Additional aspects, advantages, and features of the invention are set forth in part in the following description. Various aspects, advantages, and features of the invention will become apparent to those skilled in the art upon examination of the description and by practice of the invention.